Process for bleaching textile fibres and new bleaching compositions



The present invention relates to new bleaching compo- United States Patent sitions "for textile fibres' and more particularly to solid and stable compositions Which, in aqueous solution, give oxidising agents having high activity and which are effective at only slightly raised temperatures.

Itis known that the organic peracids and their salts have the properties of bleaching vegetable, animal or synthetic textile fibres, but the use thereof in practice is made diflicult. because such materials cannot be satisfactorily and sometimes because of their liquid condition.

The preparation in situ of organic peracids by the action of a compound yielding active oxygen to the acids or corresponding anhydrides is known, and different processes employ the peroxidation reactions of this type.

The use of carboxylic acid anhydrides in the presence of a peroxide;:compound is described in the United States Patent No. 2,284,477 issued February 5, 1940.

Solid compositions containing a mineral per salt associated with an organic anhydride are mentioned in the United States patent specification No. 2,362,401 issued September 22, 1941.

The anhydrides employed in these known processes are simple unsubstituted anhydrides, such as benzoic, phthalic, succinic, maleic, glutaric, acetic, propionic and like anhydrides. The use thereof presents various disadvantages, however, particularly when they must be employed for bleaching operations at normal temperatures and at pH values below 10.

The anhydrides of lower monoacids such as acetic, propionic and butyric acids are liquid at normal temperatures andthus are not suitable for the preparation of solid bleaching compounds ready for use.

Among the solid anhydrides, certain of them, such as the benzoic and phthalic anhydrides, have very low solubility in aqueous media and this limits the peroxidation reaction and gives a heterogeneous character to the bleaching. Certain dicarboxylic acid anhydrides have the serious disadvantage of having little reactivity in weakly alkaline medium at the relatively low temperature of 50 to 80 C.; this is the case with tetrahydrophthalic and maleic anhydrides, which only form a small amount of organic per compounds in aqueous medium. In the case of numerous solid anhydrides, the oxygen of the initial per compound is thus not satisfactorily utilized.

According to the present invention, these disadvantages are. overcome by using a process for bleaching textile fibres by immersion in a bleaching bath containing a peroxide compound, characterised by adding additionally to thebleaching bath a dicarboxylic acid anhydride, in the molecule of which at least one hydrogen atom is re placed by an electronegative group.

It has been found that the bleaching power of mixtures based on solid anhydrides of dicarboxylic acids and per compounds is considerably increased if one or more hydrogen atoms in the anhydride molecule, are replaced by an electrophilic radical such as N0 Cl, Br, H50 and NaSO These substitutions increase the reactivity of the anhydrides in the bleaching baths, particularly at temperatures between 30 and 80 C., and at pH values from 7 to 10, and the dissolution of the corresponding anhydrides is accelerated.

3,298,775 Patented.Jan. 17, 1967 The substituted phthalic anhydrides have the advantage of being solid and stable products which can be easily obtained from an industrial material. The solubility in water of the corresponding acids, particularly the solubility of nitrophthalic acids, is very much higher than that of phthalic acid.

The anhydrides of organic diacids ofiering particular interest are the nitrophthalic anhydrides, preferably 3- nitrophthalic anhydride, and the halophthalic anhydrides, such as 4-chlorophthalic anhydride.

These products are used individually or in admixture.

They are obtained from the phthalic anhydride by nitra- W tion or chlorination by the conventional methods.

The substituted anhydrides react with the hydrogen peroxide, even in weakly alkaline medium, in order to form corresponding peracids much more completely than the unsubstituted phthalic anhydride. With the object of obtaining an oxidising mixture which forms in aqueous solution, it is possible to mix beforehand, in the solid state, the substituted phthalic anhydride and a solid source of active oxygen, such as: monohydrated or tetrahydrated perborate, percarbonate, perpyrophosphate, urea peroxyhydrate and in general the mineral or organic peroxyhydrates, as well as the mineral or organic peroxides.

It is also possible to supply the substituted anhydride and the liquid hydrogen peroxide in the liquid form or in the form of peroxyhydrate separately to the bleaching solution at the moment of use.

The active oxygen concentration of the bleaching bath is preferably between 20 and 500 mg. of active oxygen per litre. The material to be bleached is treated with a solution adjusted to a pH value between 7 and 11. There are used, per molecule of peroxide, 0.4 to 2 molecules of carboxylic acid anhydride substituted by at least one electrophilic group, preferably 0.8 to 1.5 molecules.

The bleaching can be carried out at slightly elevated temperatures, for example, in the range from 30 to C. and preferably at about 60 C.

A series of examples which illustrates the present invention in non-limitative manner is given below.

The comparative tests described in the difierent examples were carried out by measuring the decoloring power of the bleaching compounds on an aqueous solution of sulphur black, sold commercially under the trademark Sulfanol M.B.S,," used in solubilised form. It has been found that a good correlation exists between the results of this test and those of the practical bleaching experiments with a commercial alkali Washing mixture.

In the series of examples given below, a sulphur black solution with an optical density equal to 0.6 (green filter, thickness 10 mm.) is prepared; this solution is buffered to an alkaline pH value by a mixture of sodium carbonate and bicarbonate, or by any other buffering system such as those formed from sodium borate. This solution is brought to 60 C. and the per compound and the anhydride are added, separately or mixed before use, and the bleaching bath is kept at 60 C. for 20 minutes. The sample is then quickly cooled to normal temperature and its optical density is measured by colorimetry. The result is expressed as a percentage of decoloration, related to a comparison sample not provided with active oxygen and placed under the same operational conditions.

Percent, decoloration= Optical density of comparison sampleoptical density of test specimen Optical density of comparison sample The quantities of active oxygen which are used and the molecular ratios between the anhydride and active oxygen are different according to the tests, but in order to obtain comparable results, such as those described in the following examples, there are systematically employed 100 mg. of active oxygen per litre of solution and a pH value of 9.5 is used, the molar ratio between the buffering agent and the active oxygen being 5.

Example 1 Under the conditions described above, the operation takes place in the absence of organic anhydrides, using sodium borate in its monohydrated form NaBO .H O or tetrahydrated form NaBO .4H O. An average degree of decoloration of 5% is obtained. When the temperature is brought to 92 C., always under the same general conditions, the average degree of decoloration is 40%.

Example 2 Under the test conditions previously described and at a temperature of 60 C., the action of the unsubstituted anhydrides and that of the substituted dicarboxylic anhydrides are compared, the active oxygen being supplied by monohydrated sodium perborate.

The results obtained are set out in the following table:

Example 3 Under the same conditions as in Example 2, a mixture of 3-nitrophthalic and 4-nitrophthalic anhydrides is used, obtained by the mixture of acids resulting from 'a phthalic anhydride nitration by means of :a sulphonitric mixture being transformed into anhydride. For a molar ratio of 1 between the anhydride and the active oxygen, a degree of decoloration of 45% is obtained. For a molar ratio of 1.3, a degree of decoloration of 68% is obtained.

Example 4 Always under the same conditions, the degree of decoloration obtained is compared, the source of active oxygen being on the one hand monohydrated sodium perborate with 15.7% of active oxygen and on the other hand sodium percarbonate with 11.7% of active oxygen, the anhydride in both cases being a sample of 3-nitrophthalic anhydride (melting point 160-163 C.), the molar ratio between the anhydride and the active oxygen being equal to 1.3.

A degree of decoloration of 49% is obtained with the perborate and of 53 with the percarbonate.

The preservation tests carried out on the mixtures of per salts with a low degree of hydration and of substituted anhydrides have been shown to be perfectly satisfactory.

For example, a mixture formed of 3.4 parts of monohydrated sodium perborate NaBO .H O and 6.6 parts of nitrophthalic anhydride, having a decolouring power of 40%, measured by the test previously described, did not show either a lowering of its active oxygen content or a loss of decolouring power after having been stored for 2 months under normal conditions, i.e., in a standard package, and at ambient temperature.

What we claim is:

1. A process for bleaching textile fibers comprising immersion in a bleaching bath containing as a source of active oxygen a peroxygen compound and containing a source of active oxygen, comprising additionally adding to the bleaching bath a phthalic acid anhydride having in its molecule at least one hydrogen atom replaced by an electronegative group.

2. A process for bleaching textile fibers in accordance with claim 1, wherein said source of active oxygen and said phthalic acid anhydride are both solid at normal temperature and are mixed beforehand in order to form a solid and stable bleaching composition which is ready for use.

3. A process for bleaching textile fibers in accordance with claim 1, wherein the material to be bleached is treated with an aqueous solution adjusted to a pH value of 7 to 11.

4. A process for bleaching textile fibers in accordance with claim 1, wherein 0.4 to 2 molecules of said phthalic acid anhydride are used per atom of active oxygen.

5. A process for bleaching textile fibers in accordance with claim 1, wherein 0.8 to 1.5 molecules of anhydride are used per atom of active oxygen.

6. A bleaching composition for textile fibers, containing as a source of active oxygen a peroxygen compound and a phthalic acid anhydride having in its molecule at least one hydrogen atom replaced by an electronega-tive group.

7. A bleaching composition in accordance with claim 6, wherein said anhydride is a nitrophthalic anhydride.

8. A bleaching composition in accordance With claim 6, wherein said anhydride comprises a mixture of nitrophthalic anhydrides.

9. A bleaching composition in accordance with claim 6, wherein said anhydride comprises a halophthalic anhydride.

10. A bleaching composition in accordance with claim 6, wherein said anhydride is in the solid state.

11. A bleaching composition in accordance with claim 7, wherein said nitrophthalic anhydride is 3-nitrophthalic anhydride.

12. A bleaching composition in accordance with claim 7, wherein said mixture comprises 4-nitrophthalic anhydride and 3-nitrophthalic anhydride.

13. A bleaching composition in accordance with claim 9, wherein said halophthalic anhydride comprises 4-chlorophthalic anhydride.

14. A bleaching composition in accordance with claim 6, wherein said source of active oxygen is a peroxide compound.

15. A method of bleaching comprising passing textile fibers through a bleaching solution comprising a mixture of a source of active oxygen selected from the group consisting of perborates, percarbonates, perpyrophosphates, peroxyhydrates and peroxides, and a phthalic anhydride acid wherein at least one hydrogen atom in the anhydride molecule is replaced by an electrophilic radical selected from the group consisting of N0 Cl, Br, H and NaSO 16. A method in accordance with claim 15, wherein said bleaching solution is maintained at between about 30 and 80 C.

17. A method in accordance with claim 1, wherein said source of active oxygen is a peroxide compound.

No references cited.

NORMAN G. TORCHIN, Primary Examiner. J. RAUBITSCHEK, Assistant Examiner,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,298,775 January 17, 1967 Jean Malafosse et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 19, after "satisfactorily" insert preserved column 4, line 44, for the claim reference numeral "7" read 8 Signed and sealed this 24th day of October 1967.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A PROCESS FOR BLEACHING TEXTILE FIBERS COMPRISING IMMERSION IN A BLEACHING BATH CONTAINING AS A SOURCE OF ACTIVE OXYGEN A PEROXYGEN COMPOUND AND CONTAINING A SOURCE OF ACTIVE OXYGEN, COMPRISING ADDITIONALLY ADDING TO THE BLEACHING BATH A PHTHALIC ACID ANHYDRIDE HAVING IN ITS MOLECULE AT LEAST ONE HYDROGEN ATOM REPLACED BY AN ELECTRONEGATIVE GROUP.
 6. A BLEACHING COMPOSITION FOR TEXTILE FIBERS, CONTAINING AS A SOURCE OF ACTIVE OXYGEN A PEROXYGEN COMPOUND AND A PHTHALIC ACID ANHYDRIDE HAVING IN ITS MOLECULE AT LEAT ONE HYDROGEN ATOM REPLACED BY AN ELECTRONEGATIVE GROUP. 